PHOTOVOLTAIC SYSTEMS WITH VOLTAGE BALANCERS
A photovoltaic module includes N sub-modules electrically connected to each other such that the negative terminal of any one but the last sub-module is electrically connected to the positive terminal of the immediate next sub-module, and N−1 voltage balancers, each having a first terminal, a second terminal and a third terminal. The second and third terminals of any one but the last voltage balancer are electrically connected to the third and first terminal of the immediate next voltage balancer, respectively. The first terminal of the first voltage balancer is electrically connected to the positive terminal of the first sub-module. The second terminal of the last voltage balancer is electrically connected to the negative terminal of the last sub-module. The third terminal of the j-th voltage balancer is electrically connected to both the negative terminal of the j-th sub-module and the positive terminal of the (j+1)-th sub-module.
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This application claims priority to and the benefit of, pursuant to 35 U.S.C. §119(a), Chinese patent application No. 201110221423.2, filed Aug. 3, 2011, entitled “PHOTOVOLTAIC SYSTEMS WITH VOLTAGE BALANCERS”, by Gui-Song Huang, Ya-Hong Xiong and Jie Huang, the content of which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTIONThe present invention relates to a photovoltaic system, and more particularly, to a photovoltaic system that utilizes one or more voltage balancers to balance the output voltages of photovoltaic modules or sub-modules thereof.
BACKGROUND OF THE INVENTIONPhotovoltaic (PV) modules are increasingly used to generate electrical energy from energy of sunlight incident on solar cells. Typically, a PV module is formed with a plurality of solar cells 10 connected in series, which may be grouped into a number of sub-modules 20 connected in series. For example, as shown in
Due to the current-source-type behavior of solar cells 10 and the fact that the value of the solar current per cell depends on the amount of incoming light, not all current sources connected in series inside the PV module may have the same value. In order to prevent that a current of a weakest cell determines the output current of the whole PV module, bypass diodes 30 are typically used inside the PV module. As shown in
However, the disadvantage of using bypass diodes is the related default-risk of the PV module and the fact that the module is not anymore reverse-polarity. The diodes can be destroyed by polarity.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.
SUMMARY OF THE INVENTIONThe present invention, in one aspect, relates to a photovoltaic (PV) module. In one embodiment, the module includes N sub-modules, N being an integer greater than one, each sub-module having a positive terminal and a negative terminal, the N sub-modules electrically connected to each other in series such that the negative terminal of any one but the last sub-module is electrically connected to the positive terminal of the immediate next sub-module.
The module also includes N−1 voltage balancers. Each voltage balancer having a first terminal, a second terminal and a third terminal, where the second terminal of any one but the last voltage balancer is electrically connected to the third terminal of the immediate next voltage balancer; the third terminal of any one but the last voltage balancer is electrically connected to the first terminal of the immediate next voltage balancer; the first terminal of the first voltage balancer is electrically connected to the positive terminal of the first sub-module; the second terminal of the last voltage balancer is electrically connected to the negative terminal of the last sub-module; and the third terminal of the j-th voltage balancer is electrically connected to both the negative terminal of the j-th sub-module and the positive terminal of the (j+1)-th sub-module, j=1, 2, 3, . . . , (N−1).
In one embodiment, each voltage balancer has a first switch, S1, and a second switch, S2, electrically coupled between the first terminal and the second terminal; a first diode, D1, and a second diode, D2, each diode electrically coupled to a respective switch in parallel; an inductor, L, electrically coupled between the junction of the first and second switches and the third terminal; and a first capacitor, C1, electrically coupled between the first and third terminals and a second capacitor, C2, electrically coupled between the second and third terminals.
Additionally, each voltage balancer may further include a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals for driving the first and second switches S1 and S2, wherein the one or more driving signals have a compensative 50% duty cycle.
In one embodiment, each voltage balancer also has an enable logic circuit electrically coupled between the pulse generator and the first and third terminals, wherein the enable logic circuit is configured to sense input voltages V1 and V2 such that when the difference between input voltages V1 and V2 is lower than a predetermined threshold, the enable logic circuit disables the pulse generator and turn the voltage balancer off, wherein the input voltages V1 and V2 are voltages at the first and third terminals, respectively.
The PV module further includes a DC/DC converter having a positive input, a negative input, a positive output and a negative output, wherein the positive and negative inputs are electrically coupled to the positive terminal of the first sub-module and the negative terminals of the last sub-module, respectively. The DC/DC converter in one embodiment, includes a pair of switches electrically connected between the positive and negative terminals; an inductor electrically coupled between the positive output and the junction of the pair of switches; and a pair of capacitors, one capacitor electrically coupled between the positive and negative inputs, and the other electrically coupled between the positive and negative outputs, wherein the negative output is electrically connected to the negative input.
In one embodiment, each sub-module includes a plurality of PV cells electrically connected to each other in series.
In another aspect, the present invention relates to a PV system. The PV system in one embodiment includes a plurality of PV modules, each PV module defined above, the plurality of PV modules electrically connected to each other in series such that the negative terminal of any one but the last PV module is electrically connected to the positive terminal of the immediate next PV module.
The PV system also includes an inverter having a first input electrically connected to the positive terminal of the first PV module, a second input electrically connected to the negative terminal of the last PV module, a first output and a second output electrically connected to a grid/load, wherein the inverter has a maximum power point tracking (MPPT) function.
In yet another aspect, the present invention relates to a PV module. In one embodiment, the PV module includes N sub-modules, N being an integer greater than two, each sub-module having a positive terminal and a negative terminal, the N sub-modules electrically connected to each other in series such that the negative terminal of any one but the last sub-module is electrically connected to the positive terminal of the immediate next sub-module; and N voltage balancers, each voltage balancer having a first terminal, a second terminal and a third terminal, wherein the second terminal of any one but the last voltage balancer is electrically connected to the third terminal of the immediate next voltage balancer; the third terminal of any one but the last voltage balancer is electrically connected to the first terminal of the immediate next voltage balancer; the first terminal of the first voltage balancer is electrically connected to the positive terminal of the first sub-module; the second and third terminals of the last voltage balancer are electrically connected to a B-out terminal and the negative terminal of the last sub-module, respectively; the third terminal of the j-th voltage balancer is electrically connected to both the negative terminal of the j-th sub-module and the positive terminal of the (j+1)-th sub-module, j=1, 2, 3, . . . , (N−1); and the third terminal of the first voltage balancer is electrically connected to a B-in terminal.
In one embodiment, each voltage balancer has a first switch, S1, and a second switch, S2, electrically coupled between the first terminal and the second terminal; a first diode, D1, and a second diode, D2, each diode electrically coupled to a respective switch in parallel; an inductor, L, electrically coupled between the junction of the first and second switches and the third terminal; and a first capacitor, C1, electrically coupled between the first and third terminals and a second capacitor, C2, electrically coupled between the second and third terminals.
Additionally, each voltage balancer may further include a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals for driving the first and second switches S1 and S2, wherein the one or more driving signals have a compensative 50% duty cycle.
In one embodiment, each voltage balancer also has an enable logic circuit electrically coupled between the pulse generator and the first and third terminals, wherein the enable logic circuit is configured to sense input voltages V1 and V2 such that when the difference between input voltages V1 and V2 is lower than a predetermined threshold, the enable logic circuit disables the pulse generator and turn the voltage balancer off, wherein the input voltages V1 and V2 are voltages at the first and third terminals, respectively.
In one embodiment, each sub-module comprises a plurality of PV cells electrically connected to each other in series.
In a further aspect, the present invention relates to a PV system. In one embodiment, the PV system comprises a plurality of PV modules, each PV module as set forth above, the plurality of PV modules electrically connected to each other such that the negative terminal and the B-out terminal of any one but the last PV module is electrically connected to the positive terminal and the B-in terminal of the immediate next PV module, respectively; and an inverter having a first input electrically connected to the positive terminal of the first PV module, a second input electrically connected to the negative terminal of the last PV module, a first output and a second output electrically connected to a grid/load, wherein the inverter has an MPPT function.
In yet a further aspect, the present invention relates to a PV system. In one embodiment, the PV system includes a plurality of PV modules, each PV module having a positive terminal and a negative terminal, the plurality of PV modules electrically connected to each other in series such that the negative terminal of any one but the last PV module is electrically connected to the positive terminal of the immediate next PV module; one or more voltage balancers, each voltage balancer having a first terminal, a second terminal and a third terminal; and an inverter having a first input electrically connected to the positive terminal of the first PV module, a second input electrically connected to the negative terminal of the last PV module, a first output and a second output electrically connected to a grid/load, wherein the inverter has an MPPT function.
In one embodiment, each voltage balancer has a first switch, S1, and a second switch, S2, electrically coupled between the first terminal and the second terminal; a first diode, D1, and a second diode, D2, each diode electrically coupled to a respective switch in parallel; an inductor, L, electrically coupled between the junction of the first and second switches and the third terminal; and a first capacitor, C1, electrically coupled between the first and third terminals and a second capacitor, C2, electrically coupled between the second and third terminals.
Additionally, each voltage balancer may further include a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals for driving the first and second switches S1 and S2, wherein the one or more driving signals have a compensative 50% duty cycle.
In one embodiment, each voltage balancer also has an enable logic circuit electrically coupled between the pulse generator and the first and third terminals, wherein the enable logic circuit is configured to sense input voltages V1 and V2 such that when the difference between input voltages V1 and V2 is lower than a predetermined threshold, the enable logic circuit disables the pulse generator and turn the voltage balancer off, wherein the input voltages V1 and V2 are voltages at the first and third terminals, respectively.
In one embodiment, each sub-module comprises a plurality of PV cells electrically connected to each other in series.
In one embodiment, each PV module comprises a plurality of sub-modules electrically connected to each other in series, each sub-module comprising a plurality of PV cells electrically connected to each other in series.
These and other aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be effected without departing from the spirit and scope of the novel concepts of the disclosure.
The accompanying drawings illustrate one or more embodiments of the invention and together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment, and wherein:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” or “has” and/or “having” when used herein, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, “around”, “about” or “approximately” shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term “around”, “about” or “approximately” can be inferred if not expressly stated.
The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings in
Referring to
The PV module 100 also includes (N−1) voltage balancers, {VBk}, k=1, 2, 3, . . . , (N−1). Each voltage balancer VBk has a first terminal (+), a second terminal (−) and a third terminal (B). The second terminal (−) of any one but the last voltage balancer is electrically connected to the third terminal (B) of the immediate next voltage balancer. The third terminal (B) of any one but the last voltage balancer is electrically connected to the first terminal (+) of the immediate next voltage balancer. Further, the first terminal (+) of the first voltage balancer VB1 is electrically connected to the positive terminal (+) of the first sub-module PV1. The second terminal (−) of the last voltage balancer VB(N−1) is electrically connected to the negative terminal (−) of the last sub-module PVN. The third terminal (B) of the k-th voltage balancer VBk is electrically connected to both the negative terminal (−) of the k-th sub-module PVk and the positive terminal (+) of the (k+1)-th sub-module PV(k+1).
For example, as shown in
Referring to
Additionally, each voltage balancer VBk also has a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals with a compensative 50% duty cycle for driving the first and second switches S1 and S2. The voltage balancer VBk provides the balancer function for the sub-modules {PVk} connected to it.
In one embodiment shown in
For such a configuration, if one sub-module is partially shaded, the current output from the sub-module may decrease, however, the voltages V1 and V2 keep the same because of the voltage balancer VBk. The PV module 100 enables each sub-module PVk to operate close to the maximal output power, even in a partial shading condition. Referring to
The PV system 600 also includes an inverter 610 having a first input port 612 electrically connected to the positive terminal (+) of the first PV module 100, a second input port 614 electrically connected to the negative terminal (−) of the last PV module 100. The inverter 610 has an output port 615 for outputting the power to a grid/load. The inverter 610 has a maximum power point tracking (MPPT) function for optimizing the power output of the PV system 600.
Referring to
For the PV module 700, the first, second and third voltage balancers VB1, VB2 and VB3 are used to balance the voltages of the three sub-modules PV1, PV2 and PV3, while the third voltage balancer VB3 is adapted for keeping the voltage balance between the second sub-module PV2 of the PV module 700 and the first sub-module PV1 of the immediately next PV module in a PV system.
The PV system 800 also includes an inverter 810 having a first input port 812 electrically connected to the positive terminal (+) of the first PV module 100, a second input port 814 electrically connected to the negative terminal (−) of the last PV module 100. The inverter 810 has an output port 815 for outputting the power to a grid or a load. The inverter 810 has an MPPT function for optimizing the power output of the PV system 800.
Referring to
In this exemplary embodiment shown in
Further, the PV system 900 includes an inverter 910 having a first input port 912 electrically connected to the positive terminal (+) of the first PV module 100, a second input port 914 electrically connected to the negative terminal (−) of the last PV module 100. The inverter 910 has an output port 915 for outputting the power to a grid or a load. The inverter 910 has an MPPT function for optimizing the power output of the PV system 900.
In sum, the present invention, among other things, recites a PV module that utilizes one or more voltage balancers to balance the output voltages of PV sub-modules thereof and applications of same.
The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.
The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to activate others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.
Claims
1. A photovoltaic (PV) module, comprising:
- (a) N sub-modules, N being an integer greater than one, each sub-module having a positive terminal and a negative terminal, the N sub-modules electrically connected to each other in series such that the negative terminal of any one but the last sub-module is electrically connected to the positive terminal of the immediate next sub-module; and
- (b) N−1 voltage balancers, each voltage balancer having a first terminal, a second terminal and a third terminal, wherein the second terminal of any one but the last voltage balancer is electrically connected to the third terminal of the immediate next voltage balancer; the third terminal of any one but the last voltage balancer is electrically connected to the first terminal of the immediate next voltage balancer; the first terminal of the first voltage balancer is electrically connected to the positive terminal of the first sub-module; the second terminal of the last voltage balancer is electrically connected to the negative terminal of the last sub-module; and the third terminal of the j-th voltage balancer is electrically connected to both the negative terminal of the j-th sub-module and the positive terminal of the (j+1)-th sub-module, j=1, 2, 3,..., (N−1).
2. The PV module of claim 1, wherein each voltage balancer comprises:
- (a) a first switch, S1, and a second switch, S2, electrically coupled between the first terminal and the second terminal;
- (b) a first diode, D1, and a second diode, D2, each diode electrically coupled to a respective switch in parallel;
- (c) an inductor, L, electrically coupled between the junction of the first and second switches and the third terminal; and
- (d) a first capacitor, C1, electrically coupled between the first and third terminals and a second capacitor, C2, electrically coupled between the second and third terminals.
3. The PV module of claim 2, wherein each voltage balancer further comprises a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals for driving the first and second switches S1 and S2, wherein the one or more driving signals have a compensative 50% duty cycle.
4. The PV module of claim 3, wherein each voltage balancer further comprises an enable logic circuit electrically coupled between the pulse generator and the first and third terminals, wherein the enable logic circuit is configured to sense input voltages V1 and V2 such that when the difference between input voltages V1 and V2 is lower than a predetermined threshold, the enable logic circuit disables the pulse generator and turn the voltage balancer off, wherein the input voltages V1 and V2 are voltages at the first and third terminals, respectively.
5. The PV module of claim 1, further comprising a DC/DC converter having a positive input, a negative input, a positive output and a negative output, wherein the positive and negative inputs are electrically coupled to the positive terminal of the first sub-module and the negative terminals of the last sub-module, respectively.
6. The PV module of claim 5, wherein the DC/DC converter comprises: wherein the negative output is electrically connected to the negative input.
- (a) a pair of switches electrically connected between the positive and negative terminals;
- (b) an inductor electrically coupled between the positive output and the junction of the pair of switches; and
- (c) a pair of capacitors, one capacitor electrically coupled between the positive and negative inputs, and the other electrically coupled between the positive and negative outputs,
7. The PV module of claim 1, wherein each sub-module comprises a plurality of PV cells electrically connected to each other in series.
8. A PV system, comprising:
- (a) a plurality of PV modules, each PV module defined in claim 1, the plurality of PV modules electrically connected to each other in series such that the negative terminal of any one but the last PV module is electrically connected to the positive terminal of the immediate next PV module; and
- (b) an inverter having a first input electrically connected to the positive terminal of the first PV module, a second input electrically connected to the negative terminal of the last PV module, a first output and a second output electrically connected to a grid or a load, wherein the inverter has a maximum power point tracking (MPPT) function.
9. A photovoltaic (PV) module, comprising:
- (a) N sub-modules, N being an integer greater than two, each sub-module having a positive terminal and a negative terminal, the N sub-modules electrically connected to each other in series such that the negative terminal of any one but the last sub-module is electrically connected to the positive terminal of the immediate next sub-module; and
- (b) N voltage balancers, each voltage balancer having a first terminal, a second terminal and a third terminal, wherein the second terminal of any one but the last voltage balancer is electrically connected to the third terminal of the immediate next voltage balancer; the third terminal of any one but the last voltage balancer is electrically connected to the first terminal of the immediate next voltage balancer; the first terminal of the first voltage balancer is electrically connected to the positive terminal of the first sub-module; the second and third terminals of the last voltage balancer are electrically connected to a B-out terminal and the negative terminal of the last sub-module, respectively; the third terminal of the j-th voltage balancer is electrically connected to both the negative terminal of the j-th sub-module and the positive terminal of the (j+1)-th sub-module, j=1, 2, 3,..., (N−1); and the third terminal of the first voltage balancer is electrically connected to a B-in terminal.
10. The PV module of claim 9, wherein each voltage balancer comprises:
- (a) a first switch, S1, and a second switch, S2, electrically coupled between the first terminal and the second terminal;
- (b) a first diode, D1, and a second diode, D2, each diode electrically coupled to a respective switch in parallel;
- (c) an inductor, L, electrically coupled between the junction of the first and second switches and the third terminal; and
- (d) a first capacitor, C1, electrically coupled between the first and third terminals and a second capacitor, C2, electrically coupled between the second and third terminals.
11. The PV module of claim 10, wherein each voltage balancer further comprises a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals for driving the first and second switches S1 and S2, wherein the one or more driving signals have a compensative 50% duty cycle.
12. The PV module of claim 11, wherein each voltage balancer further comprises an enable logic circuit electrically coupled between the pulse generator and the first and third terminals, wherein the enable logic circuit is configured to sense input voltages V1 and V2 such that when the difference between input voltages V1 and V2 is lower than a predetermined threshold, the enable logic circuit disables the pulse generator and turn the voltage balancer off, wherein the input voltages V1 and V2 are voltages at the first and third terminals, respectively.
13. The PV module of claim 9, wherein each sub-module comprises a plurality of PV cells electrically connected to each other in series.
14. A PV system, comprising:
- (a) a plurality of PV modules, each PV module defined in claim 9, the plurality of PV modules electrically connected to each other such that the negative terminal and the B-out terminal of any one but the last PV module are electrically connected to the positive terminal and the B-in terminal of the immediate next PV module, respectively; and
- (b) an inverter having a first input electrically connected to the positive terminal of the first PV module, a second input electrically connected to the negative terminal of the last PV module, a first output and a second output electrically connected to a grid or a load, wherein the inverter has a maximum power point tracking (MPPT) function.
15. A PV system, comprising:
- (a) a plurality of PV modules, each PV module having a positive terminal and a negative terminal, the plurality of PV modules electrically connected to each other in series such that the negative terminal of any one but the last PV module is electrically connected to the positive terminal of the immediate next PV module;
- (b) one or more voltage balancers, each voltage balancer having a first terminal, a second terminal and a third terminal coupled to respective PV modules for balance voltages of the respective PV modules; and
- (c) an inverter having a first input electrically connected to the positive terminal of the first PV module, a second input electrically connected to the negative terminal of the last PV module, a first output and a second output electrically connected to a grid or a load, wherein the inverter has a maximum power point tracking (MPPT) function.
16. The PV module of claim 15, wherein each voltage balancer comprises:
- (a) a first switch, S1, and a second switch, S2, electrically coupled between the first terminal and the second terminal;
- (b) a first diode, D1, and a second diode, D2, each diode electrically coupled to a respective switch in parallel;
- (c) an inductor, L, electrically coupled between the junction of the first and second switches and the third terminal; and
- (d) a first capacitor, C1, electrically coupled between the first and third terminals and a second capacitor, C2, electrically coupled between the second and third terminals.
17. The PV module of claim 16, wherein each voltage balancer further comprises a pulse generator electrically coupled to the first and second switches S1 and S2 for providing one or more driving signals for driving the first and second switches S1 and S2, wherein the one or more driving signals have a compensative 50% duty cycle.
18. The PV module of claim 17, wherein each voltage balancer further comprises an enable logic circuit electrically coupled between the pulse generator and the first and third terminals, wherein the enable logic circuit is configured to sense input voltages V1 and V2 such that when the difference between input voltages V1 and V2 is lower than a predetermined threshold, the enable logic circuit disables the pulse generator and turn the voltage balancer off, wherein the input voltages V1 and V2 are voltages at the first and third terminals, respectively.
19. The PV module of claim 15, wherein each PV module comprises a plurality of sub-modules electrically connected to each other in series, each sub-module comprising a plurality of PV cells electrically connected to each other in series.
Type: Application
Filed: Oct 3, 2011
Publication Date: Feb 7, 2013
Applicant: DELTA ELECTRONICS (SHANGHAI) CO., LTD. (Shanghai)
Inventors: Gui-Song Huang (Shanghai), Ya-Hong Xiong (Shanghai), Jie Huang (Shanghai)
Application Number: 13/251,733
International Classification: H02J 1/00 (20060101);